US4848906A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Multiplexed fiber optic sensor
Assignee: Northrop Grumman Guidance and Electronics Co Inc
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Filing: 1987-02-02
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Granted: 1989-07-18
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Expires: 2007-02-02
Abstract
Abstract An all fiber optic hydrophone or sensor array has significant size, cost, reliability, and operational advantages over other hydrophone arrays. The array comprises a distributed network of appropriately coiled optical fiber encased in commercially available marine cable. The terminal end of the sensor array preferably contains a modulated miniature solid-state laser diode and photodetector matrix which mate to power and multiplexing electronics. The distributed sensor assembly itself is entirely passive. The hydrophone array comprises an optical signal source and at least one transmitting optical fiber for guiding signals output from the optical signal source. The array further includes a plurality of sensing interferometers coupled to the transmit optical fiber and means for measuring differential changes in the optical path of each sensing interfereometer. The hydrophone array comprises means for superimposing signals output from each sensing interferometer, and a detector for converting optical signals in the receive fiber into electrical signals. The signal processing system in the array includes a compensating interferometer having optical phase modulating means formed in one arm thereof.
Inventors
- 👤 Michael R. Layton
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 09:41
CPC Classifications
G; G01; G01M; G01M11/00; G01M11/30; G01M11/39; G01H; G01H9/00; G01H9/004; G01V; G01V1/00; G01V1/16; G01V1/20; G01V1/201
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
123 words
A low power all fiber optic hydrophone array, comprising: an optical signal source; a transmitting optical fiber for guiding signals output from the optical signal source; a plurality of sensing interferometers coupled to the transmit optical fiber, each sensing interferometer having a short arm and a long arm; a receive fiber coupled to each of the sensing interferometers; and means for measuring differential changes in the optical path of each sensing interferometer, including: means for superimposing signals output from each sensing interferometer; a detector for converting optical signals in the receive fiber into electrical signals a transmit interferometer formed in the transmit fiber between the optical source and the sensing interferometer; and means formed in the transmit interferometer for modulating the optical waves.
Claim 2
Dependent Claim
123 words
A low power all fiber optic hydrophone array, comprising: an optical signal source; a transmitting optical fiber for guiding signals output from the optical signal source; a plurality of sensing interferometers coupled to the transmit optical fiber, each sensing interferometer having a short arm and a long arm; a receive fiber coupled to each of the sensing interferometers; and means for measuring differential changes in the optical path of each sensing interferometer, including: means for superimposing signals output from each sensing interferometer; a detector for converting optical signals in the receive fiber into electrical signals a transmit interferometer formed in the transmit fiber between the optical source and the sensing interferometer; and means formed in the transmit interferometer for modulating the optical waves.
Claim 3
Dependent Claim
49 words
The hydrophone array of claim 1 wherein each sensing interferometer has a pair of sensing optical paths having a predetermined path difference therebetween and wherein the transmit interferometer has a pair of optical paths that have the same path difference as the predetermined path difference of each sensing interferometer.
Claim 4
Dependent Claim
133 words
The hydrophone array of claim 1, further including: a detector array that includes a detector corresponding to each sensing interferometer for producing output electrical signals indicative of optical signals output from each of the sensing interferometers; a first mixing array connected to the detector array to receive electrical signals output therefrom; a second mixing array connected to the detector array to receive electrical signals output therefrom; oscillator means for driving the frequency shifter, said oscillator means being connected to the second mixing array, the second mixing array providing outputs indicative of the sines of the phase differences of the sensing interferometers; and phase shifting means connected between the oscillator means and the first mixing array, the first mixing array providing outputs indicative of the cosines of the phase differences of the sensing interferometers.
Claim 5
Independent Claim
127 words
A method for forming a low power all fiber optic hydrophone array, comprising the steps of: providing an optical signal source; guiding signals output from the optical signal source along a transmit optical fiber; coupling a plurality of sensing interferometers to the transmit optical fiber; forming each sensing interferometer to have a short arm and a long arm; coupling a receive fiber to each of the sensing interferometers; and measuring differential changes in the optical path of each sensing interferometer by the steps of: superimposing signals output from each sensing interferometer; converting optical signals in the receive fiber into electrical signals; forming a transmit interferometer in the transmit fiber between the optical source and the sensing interferometers; and forming optical wave modulating means in the transmit interferometer.
Claim 6
Independent Claim
127 words
A method for forming a low power all fiber optic hydrophone array, comprising the steps of: providing an optical signal source; guiding signals output from the optical signal source along a transmit optical fiber; coupling a plurality of sensing interferometers to the transmit optical fiber; forming each sensing interferometer to have a short arm and a long arm; coupling a receive fiber to each of the sensing interferometers; and measuring differential changes in the optical path of each sensing interferometer by the steps of: superimposing signals output from each sensing interferometer; converting optical signals in the receive fiber into electrical signals; forming a transmit interferometer in the transmit fiber between the optical source and the sensing interferometers; and forming optical wave modulating means in the transmit interferometer.
Claim 7
Dependent Claim
55 words
The method of claim 4 further including the steps of: forming each sensing interferometer to have a pair of sensing optical paths having a predetermined path difference therebetween; and forming the transmit interferometer to have a pair of optical paths that have the same path difference as the predetermined path difference of each sensing interferometer.
Claim 8
Dependent Claim
141 words
The method of claim 4, further including the steps of: forming a detector array that includes a detector corresponding to each sensing interferometer for producing output electrical signals indicative of optical signals output from each of the sensing interferometers; connecting a first mixing array to the detector array to receive electrical signals output therefrom; connecting a second mixing array to the detector array to receive electrical signals output therefrom; driving the frequency shifter with the oscillator means, connecting the oscillator means to the second mixing array, so that the second mixing array provides outputs indicative of the sines of the phase differences of the sensing interferometers; and connecting the phase shifting means between the oscillator means and the first mixing array so that the first mixing array provides outputs indicative of the cosines of the phase differences of the sensing interferometers.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1992-07-17 | 1993-01-16 | 1993-07-18 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1996-07-17 | 1997-01-16 | 1997-07-18 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2000-07-17 | 2001-01-16 | 2001-07-18 | $7700.00 | Window Closed / Lapsed |